This invention relates generally to a tamper evident closure for a container in which a liner sealed over the container opening ruptures and is visually indicated incident to any attempt to remove the closure cap.
Most containers of, for example, medicants and comestibles have a moisture proof cap liner overlying the mouth of the container opening. The liner may be bonded to the container surrounding the opening so as to require the user to rupture or peel away the liner after cap removal to gain access to the container contents. And, any tampering with the container will be made self evident if the liner has been punctured or ruptured. However, once the cap is removed it is entirely possible that tampering could go unnoticed if the liner were to be carefully removed and replaced.
To avoid this drawback, various tamper evident closures have been developed such as that disclosed in U.S. Pat. No. 4,553,678 in which indicating film is applied to either the base of the container neck or to the underside of the container cap end wall such that, upon cap rotation, engagement of a cap flange or the projecting fingers of a separate bias spring with the film will rupture or score the same rendering any container tampering clearly visible.
U.S. Pat. No. 4,576,297 disclosed another tamper evident closure in which a cover of translucent material overlies the container liner bonded to the surface of the container which surrounds its opening, a spot of adhesive adhering the inside of the cover to the liner and being laterally offset from the central axis of the cover. Upon relative movement between the cover and the container the liner is caused to tear by the spot of adhesive to provide visual indication that the cap has been previously removed.
These prior approaches taken in evidencing a tampering or a previously open condition of the container are, however, not without their drawbacks. For example, tamper indicating material must be either specially applied to the base of the container neck, or if applied to the underside of the cap end wall a separate bias spring having projecting fingers must be employed. Otherwise, a torn or ruptured container liner may not always be visible to an unsuspecting operator even through a translucent cap. Besides, since both the aforementioned closure caps give immediate indication of tampering upon cap rotation, they are unsuitable for those closures in which it may be desirable to permit cap rotation without tamper indicating and before cap removal for non-screw caps such as those snap caps which must be rotated to a position of matching arrows between the cap and container before the cap is lifted off.